JPH021321A - liquid jet recording head - Google Patents

Abstract

PURPOSE:To improve durability of a heat accumulation layer and to extend a life of a heating part by taking a material of the heat accumulation layer on a passage base plate as SiOx (where 1.8<=X<=2.0) in a thermal energy operating part of an ink jet recording head. CONSTITUTION:A heat accumulation layer 33, a heating resistor 29, and a pair of electrodes 27, 28 connected thereto are laminated on a heating element base plate 22 in a thermal energy operating part annexed to a passage by which an orifice 24 of a recording head, a recording liquid inflow port 23 and a liquid chamber are interconnected with one another. Further protective layers 34, 35 are respectively provided so that the heating resistor layer 29 and the electrodes 27, 28 are not brought into contact with recording liquid. Furthermore, by making material of said heat insulating layer of SiOx (where 1.8<=X<=2.0) which is low in thermal conducting and excellent in insulating property, durability of a heating part which is continuously driven at high speed is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a heat storage layer in a heat generating portion of a liquid jet recording head, and more particularly to a bubble diene 1-type ink jet recording head.

Conventional non-impact recording methods have recently attracted attention because the noise generated during recording is so small that it can be ignored. Among them, high-speed recording is possible,
The so-called Infusiera 1 recording method, which allows recording on so-called plain paper without the need for special fixing treatment, is an extremely powerful recording method, and various methods have been proposed and improvements have been made. Some have been commercialized, and efforts are still being made to put them into practical use.

In this type of inkjet recording method, recording is performed by causing droplets of a recording liquid called ink to fly and adhere to a recording member. There are several types of methods depending on the control method used to control the flight direction of the generated recording liquid droplets.

The first method is, for example, the one disclosed in USP No. 3,060,429 (Teletype method), in which droplets of recording liquid are generated by electrostatic attraction, and the generated droplets of recording liquid are used for recording. Recording is performed by controlling an electric field in accordance with a signal to selectively attach recording liquid droplets onto a recording member.

To explain this in more detail, an electric field is applied between the nozzle and the accelerating electrode to eject a small amount of negatively charged recording liquid from the nozzle, and the ejected small droplet of the recording liquid responds to the recording signal. The droplet is caused to fly between x and y deflection electrodes configured to be electrically controllable, and the droplet is selectively attached to the recording member by changing the intensity of the electric field to perform recording.

The second method is a method (Sweet method) disclosed in, for example, USP No. 3,596,275, USP No. 3,298,030, etc., and uses a small amount of recording liquid whose charge amount is controlled by a continuous vibration generation method. Recording is performed on the recording member by generating droplets and flying the generated band flu controlled droplets between the deflection poles '11i' to which a -like electric field is applied.

Collectively, the orifice (discharge port) of the nozzle is a part of the recording head to which the piezo vibrating element is attached.
A charged electrode configured to have a recording signal applied thereto is arranged at a predetermined distance in front of the piezo vibrating element, and an electric signal of a constant frequency is applied to the piezo vibrating element to mechanically vibrate the piezo vibrating element, A small droplet of recording liquid is ejected from the ejection port. At this time, a charge is electrostatically induced in the recording liquid droplet discharged by the charging electrode, and the droplet is charged with an amount of 11 charges corresponding to the recording signal. 'IiF When a small droplet of recording liquid with a controlled amount of charge flies between deflection electrodes to which a constant electric field is uniformly applied, it is deflected according to the amount of charge added, and the small droplet that carries the recording signal Only drops can be deposited on the recording member.

The third method is, for example, the method disclosed in USP No. 3,416,153 (llcrtz method), in which an electric field is applied between a nozzle and a ring-shaped charging electrode, and small droplets of recording liquid are generated by a continuous vibration generation method. This is a method that generates atomized light and records it. In other words, with this method, 1 nozzle and band? By modulating the electric field strength applied between electrodes Ii in accordance with the recording signal, the atomization state of the droplets is controlled, and the gradation of the recorded image is produced and recorded.

The fourth method is, for example, the method disclosed in USP No. 3,747,120 (Stemme method), and this method is fundamentally different in principle from the above three methods.

That is, in all three methods, the droplets of recording liquid ejected from the nozzle are electrically controlled while they are in flight, and the droplets carrying the recording signal are selectively attached to the recording member. In contrast, recording is performed by

The Sternmc method performs recording by ejecting a small amount of recording liquid from an ejection port in response to a recording signal.

In other words, the Stemme method applies an electrical recording signal to a piezo vibrating element attached to a recording head that has an ejection port for discharging recording liquid, and converts this electrical recording signal into mechanical vibration of the piezo vibrating element. In contrast, recording is performed by ejecting a small amount of recording liquid from the ejection port and adhering it to the recording member according to the mechanical imaging.

These four conventional methods each have their own advantages, but there are also points that can be solved in the other method.

That is, in the first to third methods, the direct energy for generating droplets of the recording liquid is electrical energy, and the deflection control of the droplets is also electric field control.

Therefore, although the first method is simple in structure, it requires a high voltage to generate small particles, and it is difficult to use a multi-nozzle recording head, making it unsuitable for high-speed recording. .

The second method allows the recording head to have multiple nozzles and is suitable for high-speed recording, but it has a complicated structure, and it is difficult to control the recording liquid droplets in a 1" range. There are problems such as the tendency for satellite dots to occur on the top.

The third method has the advantage that images with excellent gradation can be recorded by atomizing recording liquid droplets, but on the other hand, it is difficult to control the atomization state.

There are various problems such as fogging in the recorded image, difficulty in forming a recording head with multiple nozzles, and unsuitability for high-speed recording.

The fourth method has relatively many advantages compared to the first to third methods. In other words, the configuration is simple, and since recording is performed by ejecting the recording liquid from the ejection opening of the nozzle on-demand, it is possible to use a small droplet that flies as in the first to third methods. , it is not necessary to collect the quotient not required for recording the image, and as in the first and second methods.

It has great advantages such as there is no need to use a conductive liquid and there is a large degree of freedom regarding the material of the recording liquid.

On the other hand, it is difficult to make the recording head multi-nozzle because there are problems in processing the recording head, and it is extremely difficult to miniaturize the piezoelectric vibrating element having the desired resonance number. This method has drawbacks such as that it is not suitable for high-speed recording because the recording liquid droplets are ejected and ejected in flight using the mechanical energy of the mechanical vibration of the piezoelectric vibrating element.

In this way, conventional methods have problems in terms of structure and high-speed recording.

The use of multi-nozzle recording heads has advantages and disadvantages in terms of the generation of satellite dots and fogging of recorded images, and there is a restriction that it can only be applied to applications that take advantage of these advantages.

Further, Japanese Patent Application Laid-Open No. 55-123478 proposes providing a thermal energy generating means in a so-called bubble jet liquid jet recording device on a substrate having a thin film of low thermal conductivity.

FIG. 6 is a diagram for explaining in detail the thermal energy invention disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 55-123478.
The heating resistor 11 is made of a substrate 12 with high thermal conductivity;
A thin film 13 with low thermal conductivity is coated, and a heating element layer 1 is further coated.
4 and an electrode layer 15 for applying a signal from the outside.
It is formed by

In the figure, the part marked (■) is the heating part. Also, 16 is a protective film, which protects the heating element layer, electrodes, etc., or provides insulation when the recording medium liquid comes into direct contact with the nuclear heating resistor.] The material of the substrate 12 is as follows.
For example, metals such as AQ, Cu, or AQ20. Ceramics such as

The material for the thin film laminated on the substrate must be such that it does not undergo thermal deterioration within the elevated temperature range near the heating element layer, that it can form a uniform layer, and that it has the following properties: to improve responsiveness, energy efficiency, etc. It is required that a layer of about 0.1 to 10 μm can be easily formed on the substrate, and that it has sufficient adhesion to other layers (heat generating layer, substrate, etc.) in a laminated state. In addition, its thermal conductivity value is 0.6k at a temperature around room temperature.
cal/mhr'c or less, preferably 0.05 to 0.4
kcal, /m h r 'C is used.

Furthermore, considering the amount of signal energy applied to the heating resistor, the interval of signal application time, etc., a material satisfying the above conditions is usually used with a thickness of 0.1 to 10 μm, preferably Q, 3 to 1.
It is desirable to form the groove to a thickness of 0 prn, optimally in the range of 1-6 μm.

The material used may be any type of material, such as inorganic or organic materials, or in some cases, a composite material made of these materials or a plurality of laminated materials, as long as these conditions are satisfied. In particular, heat-resistant organic polymer materials having a softening point or melting point of 150° C. or higher, particularly 200° C. or higher, are preferably used.

The reasons why organic materials are effective as materials for thin films with low thermal conductivity are that they can be easily formed into thin films, that M with high adhesion to other layers can be easily obtained when laminated, and that they have good thermal conductivity. The reason for this is that the degree value is sufficiently low.

Accordingly, in the invention described in JP-A No. 55-123478, the thermal energy generating means is provided on a substrate having a thin film with low thermal conductivity. is important, but the above-mentioned Japanese Patent Application Laid-Open No. 55-1234
No. 78 does not mention durability, which is another important quality required. In particular, there is no description of heat storage JF'J made of SiOx, but in a bubble jet, the thermal energy acting part is exposed to severe heat cycles, so its durability is an important issue. This problem becomes particularly serious in a head that is continuously driven at high speed (for example, 4 kl (faster than z)).

1-1 The present invention was made in view of the above-mentioned circumstances,
In particular, this was done with the aim of improving the durability of the heat generating section of a bubble jet type inkjet recording head that is driven continuously at high speed.

Furthermore, in order to achieve the above object, the present invention contains a recording liquid to be introduced, generates bubbles in the recording liquid by heat, and uses thermal energy to generate an acting force as the volume of the bubbles increases. a flow path provided with an acting portion; an orifice communicating with the flow path for causing the recording liquid to be ejected as droplets by the acting force; and an orifice communicating with the flow path and introducing the recording liquid into the flow path. A liquid jet recording head comprising a liquid chamber for recording and a means for introducing the recording liquid into the liquid chamber, the head being continuously energized at a higher speed than 4k)lz, and the thermal energy application section having the following properties: a heat storage layer provided on the substrate; a heat generating resistor layer provided on the heat storage layer;
at least one pair of electrically connected to the heating resistor layer;
a protective layer for preventing the heat generating resistor j1 from coming into contact with the recording liquid is provided on the heat generating resistor J, and the heat storage 1+1 is described as SiOx. It is characterized by containing a substance that satisfies 1.8≦x≦2.0.Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a sectional view of a main part for explaining one embodiment of the present invention, that is, an enlarged sectional view of a thermal energy acting part, and FIG. 2 is an example of an inkjet printer 1 to a head to which the present invention is applied. 3 is a perspective view showing an example of the bubble jet head, and FIG. 4 is a diagram for explaining the operation of the bubble jet head shown in FIG. a)) and a heating element board (Fig. 4 (b)). Fig. 5 is a perspective view of the lid board shown in Fig. 4 (a) seen from the back side. , 21 is a lid substrate.

22 is a heating element substrate, 23 is a recording liquid inlet, 24 is an orifice, 25 is a channel, 26 is a region for forming a liquid chamber, 27 is an individual (independent) electrode, 28 is a common electrode, and 29 is a heating element (heater), 30 is ink, 31 is a bubble, 32 is a flying ink droplet, 33 is a heat storage layer, 34 is a heating resistor protective layer,
35 is an electrode protective layer.

First, ink ejection by a bubble jet will be described with reference to FIG. 2. (a) is a steady state, in which the surface tension of the ink 30 and the external pressure are in equilibrium on the orifice surface.

In (b), the heater 29 is heated until the surface temperature of the heater 29 rises rapidly and boiling development occurs in the adjacent ink layer, and microbubbles 31 are scattered.

In (c), the adjacent ink layer that is rapidly heated on the entire surface of the heater 29 is instantly vaporized, forming a till film, and the air bubbles 3
1 is in a grown state. At this time, the pressure inside the nozzle is
The bubbles rise as much as they grow, the balance with the external pressure on the orifice surface is lost, and the ink column begins to grow from the orifice.

(d) shows a state in which the bubble has grown to its maximum, and ink 30 corresponding to the volume of the bubble is pushed out from the orifice surface. At this time, no current is flowing through the heater 29, and the surface temperature of the heater 29 is decreasing. The maximum value of the volume of the bubble 31 is slightly delayed from the timing of electric pulse application.

(c) shows a state in which the bubbles 31 are cooled by ink or the like and begin to contract. At the tip of the ink column, it moves forward while maintaining the extruded speed, and at the rear end, the ink flows backward from the orifice surface into the nozzle due to the decrease in nozzle internal pressure as the bubbles contract, creating a constriction in the ink column. .

(I') The air bubbles 31 are contracted to J♂, and the ink comes into contact with the heater surface, causing the heater surface to be further rapidly cooled. At the orifice surface, the external pressure is higher than the nozzle internal pressure, so the meniscus is largely moving into the nozzle. The tip of the ink column turns into a droplet and flies in the direction 8M- at a speed of 5 to 10 m/sec.

In (g), the air bubbles have completely disappeared in the process of refilling the orifice with ink by capillary action and returning to the state of (a).

The present invention was developed by carefully selecting the material for the heat storage layer for Bubble Geno 1 as described above, through numerous experiments and numerous head prototypes, in order to protect the thermal energy acting part of the inkjet head from heat cycles and improve its lifetime. The purpose is to limit the composition and provide a configuration that can be truly put into practical use.

FIG. 1 is a cross-sectional view of a main part for explaining one embodiment of a liquid jet recording head according to the present invention, in other words, an enlarged cross-sectional view of a thermal energy acting part, in which a heating resistor 29 is formed in the present invention. Silicon oxide (SIOx) is selected as the material for the l-thermal layer 33. According to this principle 110, silicon oxide has low thermal conductivity and also exhibits excellent performance as an insulating material.
While bubbles are generated, the heat energy generated in the substrate side 2
This is to prevent you from running away from step 2. This heat storage layer 33 can be easily manufactured by a sputtering method, a CVD method, etc., but the most preferable method is to use silicon as the substrate 22 and to make silicon or silicon oxide (S) by thermal oxidation.
It is good to grow iOx). If a product is manufactured under easy conditions, even if it is a silicon compound, it will not be able to maintain its durability when exposed to severe heat cycles, and the thermal energy acting part may break. This problem becomes more serious as the number of repeated bee-1 cycles increases, and it is especially important for heads that are driven continuously at a speed higher than 4kl (z) for high-speed recording. In order to meet strict requirements, materials are required to:
The goal is to strictly define what (what kind of element) and how much is bonded to silicon (Si). In the present invention, the material is SiOx, where the possible values of X are 1.8≦x≦2.0, and the quality required for the material is satisfied. When forming these films, for example, even if an element that is not desired to be bonded to Si is bonded to Si, resulting in Si 0xNyHz, as long as X satisfies the above value, the heat storage layer can be formed. As the quality is satisfied and available for use.

Note that the thickness of the heat storage layer is usually 2 μm or more.

Other materials constituting the thermal energy application section will be briefly explained below.

Examples of useful materials for forming the heating resistor layer 29 include tantalum nitride and nichrome.

Examples include silver-palladium alloys, silicon semiconductors, and borides of metals such as hafnium, lanthanum, zirconium, titanium, tantalum, tungsten, molybdenum, niobium, chromium, and vanadium.

Among the materials constituting these heating resistor layers, metal borides are particularly excellent, and among these, hafnium boride has the best properties, followed by zirconium boride and hardened borides. Lanthanum, tantalum boride,
The order is vanadium boride and niobium boride.

The heating resistor J can be formed using the above-mentioned materials by techniques such as electron beam evaporation and sputtering. The film thickness of the heating resistor WJ is determined according to its area, material, shape and size of the heat-acting part, and actual power consumption, etc. so that the amount of heat generated per unit time is as desired. However, in normal cases it is 0.001~
The thickness is 5 μm, preferably 0.01 to 1 μm.

As the material constituting the electrodes 27 and 28, many commonly used electrode materials can be effectively used, and specific examples include AI, Ag, Aυ, Pt, Cu, etc. It is then provided at a predetermined location with a predetermined size, shape, and thickness using a method such as vapor deposition.

The characteristics required of the heat resistor 134 are to protect the heat generating resistor from the ink without hindering the effective transfer of the heat generated by the heat generating resistor to the recording liquid (ink). Examples of useful materials for forming the protective layer include silicon oxide, silicon nitride, magnesium oxide, aluminum oxide, tantalum oxide, and zirconium oxide, which can be prepared using methods such as electron beam evaporation and sputtering. can be formed.

The film lrX of the holding 11p no 1η is 0.01-
10μm, preferably 0.1-5μrn, optimally 0.1
It is desirable that the thickness be 3 μm.

A film was formed on a silicon substrate by sputtering using 5in2 and Ta as targets at a ratio of approximately 8:2. The film thickness is 2.5 μm. Then the first
With the configuration shown in the figure, tantalum nitride (heating element) is heated to 0.
3 μm thick, gold (electrode) 0.8 μm thick, and a protective film of the heating element made of Sin, 1 μm thick. The effective size of the heating elements is 25 μm x 100 μm, and the arrangement density is 16 pieces/m. When this was driven in ink, there was no problem with continuous pulsation at 2 kHz, but when it was driven at 5 k [Iz], it broke after a few minutes.

A 5in2 film was grown on a thin silicon substrate by thermal oxidation. At that time, a high-pressure thermal oxidation method is used to create a more dense 5i
The intended thickness for forming the N2 film is 2 μm.

The subsequent pattern formation is the same as in Example 1. When the thus produced heating element substrate was driven in ink, no abnormality was observed even when the heating element substrate was operated at 5 kHz, and more than 109 cycles were obtained.

Effects As is clear from the explanation in Section 2, the present invention has the advantage that the durability of the heat storage layer is improved and the life of the entire thermal energy application group is significantly extended.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of essential parts for explaining one embodiment of the present invention, and FIG. 2 is a diagram for explaining the operation of a bubble jet head as an example of an infusiera 1 to head to which the present invention is applied. Fig. 3 is a perspective view showing an example of a bubble jet head, Fig. 4 is an exploded perspective view, Fig. 5 is a view of the lid substrate seen from the back side, and Fig. 6 explains the prior art. This is a diagram for 22...Heating element substrate, 27.28,...Electrode, 29
... Heat generating resistor, 33... Heat storage layer, 34... Heat generating resistor protection JI'J, 35... Electrode protective layer.

Claims (1)

[Claims] 1. A flow path that accommodates the recording liquid to be introduced and is provided with a thermal energy acting section that generates bubbles in the recording liquid by heat and generates an acting force as the volume of the bubbles increases; an orifice that communicates with the flow path to eject the recording liquid as droplets by the acting force; a liquid chamber that communicates with the flow path and introduces the recording liquid into the flow path; In a liquid jet recording head comprising a means for introducing a liquid, the thermal energy application section includes a heat storage layer provided on the substrate, a heating resistor layer provided on the heat storage layer, and a heating resistor layer provided on the heat storage layer. A protective layer having at least one pair of electrically connected electrodes and preventing the heating resistor layer from coming into contact with the recording liquid is provided on the heating resistor layer, and the heat storage layer is made of SiOx.
A liquid jet recording head comprising a substance described as follows, and satisfying 1.8≦x≦2.0.